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90-43-7Relevant articles and documents
Catalyst-Free Synthesis of O-Heteroacenes by Ladderization of Fluorinated Oligophenylenes
Feofanov, Mikhail,Akhmetov, Vladimir,Takayama, Ryo,Amsharov, Konstantin
supporting information, p. 5199 - 5203 (2021/02/21)
A novel catalyst-free approach to benzoannulated oxygen-containing heterocycles from fluorinated oligophenylenes is reported. Unlike existing methods, the presented reaction does not require an oxygen-containing precursor and relies on an external oxygen source, potassium tert-butoxide, which serves as an O2? synthon. The radical nature of the reaction facilitates nucleophilic substitution even in the presence of strong electron-donating groups and enables de-tert-butylation required for the complete annulation. Also demonstrated is the applicability of the method to introduce five-, six-, and seven-membered rings containing oxygen, whereas multiple annulations also open up a short synthetic path to ladder-type O-heteroacenes and oligodibenzofurans.
Catalytic SNAr Hydroxylation and Alkoxylation of Aryl Fluorides
Kang, Qi-Kai,Li, Ke,Li, Yuntong,Lin, Yunzhi,Shi, Hang,Xu, Lun
supporting information, p. 20391 - 20399 (2021/08/13)
Nucleophilic aromatic substitution (SNAr) is a powerful strategy for incorporating a heteroatom into an aromatic ring by displacement of a leaving group with a nucleophile, but this method is limited to electron-deficient arenes. We have now established a reliable method for accessing phenols and phenyl alkyl ethers via catalytic SNAr reactions. The method is applicable to a broad array of electron-rich and neutral aryl fluorides, which are inert under classical SNAr conditions. Although the mechanism of SNAr reactions involving metal arene complexes is hypothesized to involve a stepwise pathway (addition followed by elimination), experimental data that support this hypothesis is still under exploration. Mechanistic studies and DFT calculations suggest either a stepwise or stepwise-like energy profile. Notably, we isolated a rhodium η5-cyclohexadienyl complex intermediate with an sp3-hybridized carbon bearing both a nucleophile and a leaving group.
Homogeneous Palladium-Catalyzed Selective Reduction of 2,2′-Biphenols Using HCO 2H as Hydrogen Source
Li, Ruoling,Li, Chenchen,Yang, Wen,Zhao, Wanxiang
, p. 1605 - 1618 (2021/02/01)
An efficient homogeneous palladium-catalyzed selective deoxygenation of 2,2′-biphenols by reduction of aryl triflates with HCO 2H as the hydrogen source is reported. This protocol complements the current method based on heterogeneous Pd/C-catalyzed hydrogenation with hydrogen gas. This process provided the reduction products in good to excellent yields, which could be readily converted to various synthetically useful molecules, especially ligands for catalytic synthesis.
C(acyl)-C(sp2) and C(sp2)-C(sp2) Suzuki-Miyaura cross-coupling reactions using nitrile-functionalized NHC palladium complexes
?akir, Sinem,Karabiyik, Hande,Kavukcu, Serdar Batikan,Rethinam, Senthil,Türkmen, Hayati
, p. 37684 - 37699 (2021/12/09)
Application of N-heterocyclic carbene (NHC) palladium complexes has been successful for the modulation of C-C coupling reactions. For this purpose, a series of azolium salts (1a-f) including benzothiazolium, benzimidazolium, and imidazolium, bearing a CN-substituted benzyl moiety, and their (NHC)2PdBr2 (2a-c) and PEPPSI-type palladium (3b-f) complexes have been systematically prepared to catalyse acylative Suzuki-Miyaura coupling reaction of acyl chlorides with arylboronic acids to form benzophenone derivatives in the presence of potassium carbonate as a base and to catalyse the traditional Suzuki-Miyaura coupling reaction of bromobenzene with arylboronic acids to form biaryls. All the synthesized compounds were fully characterized by Fourier Transform Infrared (FTIR), and 1H and 13C NMR spectroscopies. X-ray diffraction studies on single crystals of 3c, 3e and 3f prove the square planar geometry. Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), metal mapping analyses and thermal gravimetric analysis (TGA) were performed to get further insights into the mechanism of the Suzuki-Miyaura cross coupling reactions. Mechanistic studies have revealed that the stability and coordination of the complexes by the CN group are achieved by the removal of pyridine from the complex in catalytic cycles. The presence of the CN group in the (NHC)Pd complexes significantly increased the catalytic activities for both reactions.
Pd(II) complexes with ONN pincer ligand: Tailored synthesis, characterization, DFT, and catalytic activity toward the Suzuki-Miyaura reaction
Bagri, Sanjay Singh,Chaurasia, Bhaskar,Gaur, Pratiksha,Mehrotra, Ripul,Raidas, Mohan Lal,Shukla, Satyendra Nath
, (2020/08/25)
A pincer type ONN tridentate Schiff base ligand, 2-(((pyridin-2-yl)methylimino)methyl)-6-methoxyphenol, (L1) synthesized by the condensation of 4-hydroxy-3-methoxy-benzaldehyde and (pyridin-2-yl)methanamine. The ligand L1 and the new Pd(II) heteroleptic complexes of the composition [Pd(L1)(L2)]Cl, where L2 = benzimidazole, imidazole, benzooxazol or pyridine were synthesized and characterized by a set of chemical, spectrometric and spectroscopic analyses. These complexes were named 1 to 4, respectively. The FT-IR and DFT have suggested that ligand is coordinated with metal through azomethine-N and phenolic-O and arranged in square planar fashion around the metal. Correlation coefficients value between 0.995 - 0.993 shows satisfactory agreement in theoretical and experimental 1H-NMR and 13C-NMR. Benzimidazole anchored complex 1 exhibits an excellent catalytic activity. DFT calculated the energy profile diagram of the Suzuki-Miyaura reaction.
From the grafting of NHC-based Pd(II) complexes onto TiO2 to the in situ generation of Mott-Schottky heterojunctions: The boosting effect in the Suzuki-Miyaura reaction. Do the evolved Pd NPs act as reservoirs?
De Tovar, Jonathan,Rataboul, Franck,Djakovitch, Laurent
, p. 133 - 147 (2021/05/10)
The assumption that the real active species involved in the Suzuki-Miyaura reaction are homogeneous, heterogeneous or both is often proposed. However a lack of characterization of the true catalytic entities and their monitoring makes assumptions somewhat elusive. Here, with the aim of getting new insights into the formation of active species in the Suzuki-Miyaura reaction, a family of palladium(II) complexes bearing bis(NHC) ligands was synthesized for immobilization at the surface of TiO2. The studies reveal that once the complexes are anchored onto TiO2, the mechanism governing the catalytic reaction is different from that observed for the non-anchored complexes. All complexes evolved to Pd NPs at the surface of TiO2 under reaction conditions and released Pd species in the liquid phase. Also, this reactivity was boosted by the in situ generation of Mott-Schottky heterojunctions, opening new routes towards the design of heterogenized catalysts for their further implementation in reverse-flow reactors.
Microflowers formed by complexation-driven self-assembly between palladium(ii) and bis-theophyllines: Immortal catalyst for C-C cross-coupling reactions
Jin, Ren-Hua,Jou, Naoki,Kaikake, Katsuya,Shitara, Go
, p. 35311 - 35320 (2021/11/30)
The Pd catalyst for Suzuki-Miyaura or the other C-C coupling reactions is one of the central tools in organic synthesis related to medicine, agricultural chemicals and advanced materials. However, recycling palladium is a bottleneck for developing the extreme potential of Pd in chemistry. Herein, we established a new heterogeneous Pd catalytic system in which the catalyst is a nanopetal-gathered flower-like microsphere self-assembled from PdCl2 and alkyl-linked bis-theophyllines. The microflowers catalyzed quantitatively the reaction of aryl bromides and phenylboronic acid in aqueous media at room temperature. It was found that the reaction proceeds better in an air atmosphere than in nitrogen gas even though the Pd(ii) species employed was lowered to 0.001 mol% in the substance. Very interestingly, the microflowers could be recycled 20 times without deactivation in the C-C coupling reaction between bromobenzene and phenylboronic acid in the presence of sodium chloride. We found that the sodium chloride added played an important role in maintaining the morphology of microflowers and preventing the formation of metallic Pd particles.
Unusual Acetonitrile Adduct Formed via Photolysis of 4′-Chloro-2-Hydroxybiphenyl in Aqueous Solution
Zhang, Xiting,Guo, Yan,Dallin, Erin,Ma, Jiani,Dai, Mingdong,Phillips, David Lee
, p. 11635 - 11640 (2020/10/23)
In this work, 2,4′-dichlorobiphenyl (1) yielded 4′-chloro-2-hydroxybiphenyl (2) after photolysis in neutral acetonitrile aqueous (ACN-H2O) solutions. Ultrafast spectroscopic measurements and density functional theory (DFT) computations were performed for 2 in ACN and ACN-H2O (v/v, 1:1). These results were compared with previously published results for 2-hydroxybiphenyl (3). The counterparts 2 and 3 went through a singlet excited state intramolecular proton transfer (ESIPT) in ACN but behaved differently in ACN-H2O with a dehydrochlorination process occurring for 2 and an ESIPT taking place for 3. Computational results indicate that the phenol O-H bond elongates after photoexcitation to induce a concerted asynchronous process with the C-Cl bond increasing first followed by HCl elimination. A biradical intermediate (IM1) is then formed with some spin located at the phenyl 4′-C radical that appears to favor a hydrogen atom transfer (HAT) process and some spin located on phenoxyl that appears to prefer a subsequent a CH2CN radical rebound. The hydrogen bond promotes HCl elimination, while this is disfavored for ESIPT, making 4′-Cl extrusion the predominant process in ACN-H2O solutions. The mechanistic investigations have fundamental and significant implications for the understanding of polychlorinated biphenyl photolysis in an aqueous environment and hence the photodegradation of these kinds of pollutants in the natural environment.
Preparation method of O-hydroxybiphenyl
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Paragraph 0019-0029, (2020/06/17)
The invention relates to a preparation method of o-hydroxydiphenyl and in particular relates to a method for preparing the o-hydroxydiphenyl by opening the ring of dibenzofuran. The preparation method comprises the following steps: performing a condensation reaction on the dibenzofuran and sodium hydride at 140-250 DEG C for 1-3 hours, and preserving heat at 140-250 DEG C for 5-7 hours; after heat preservation, destroying the non-reacting sodium hydride by use of a solvent at 85-100 DEG C, and then adding water and preserving heat at 85-100 DEG C for 1-3 hours; after the heat preservation treatment, cooling to the room temperature and filtering, standing and layering the filtrate by use of an extraction filtrate, removing the organic layer, acidifying the water layer by use of an acid and standing and layering at 50-95 DEG C, dehydrating the organic layer and performing reduced pressure distillation on the organic layer to obtain the o-hydroxydiphenyl.
Ag-Catalyzed Cyclization of Arylboronic Acids with Elemental Selenium for the Synthesis of Selenaheterocycles
Gao, Wen-Xia,Huang, Xiao-Bo,Liu, Miao-Chang,Wu, Hua-Yue,Zhang, Xue,Zhou, Yun-Bing
, p. 5639 - 5644 (2020/11/30)
A general method for the synthesis of five-membered and six-membered selenaheterocycles through Ag-catalyzed C?Se bond-forming reaction is reported. This reaction proceeds via intramolecular cyclization of arylboronic acids with selenium powder. Preliminary mechanism studies demonstrate that this transformation involves a selenium-centred radical intermediate. (Figure presented.).
